As far as the SN, they say this under FOREIGN-BUILT FRAMES AND BIKES AFTER 1982: "An 8 or 9 character alphanumeric code was used for mid- and low-level frames subcontracted in Taiwan. Most of these bikes were labeled "Made in Taiwan" (although the sticker often is easily removed). This form of serial number appears to have been used during the period 1987 to 93. The number leads with a T (for Trek?) then a numeral, one letter or two, then five (sometimes 4) numerals. Sean Hickey suggested the first numeral is the year of manufacture, and the letter is the month of the year (A - L). This is confirmed by serial numbers that were submitted by other Trek owners. If there are two letters after the year numeral, the first is the month. The second runs from A through at least Y. It might be a way of extending the 5 digit number series by a factor of 26."

That's a sweet deal on that Trek. They usually flip for about $100 to $150, depending on condition. Rigid fork bikes actually bring as much or more than suspension fork bikes because folks have learned, old suspension forks frequently need to be replaced and that cost serious money. THose old rigid fork bikes are solid commuter or light MTB trail rides.